Many work machines, such as tractors, excavators, loaders, and other earth moving equipment, utilize hydraulic actuators to generate the force required to accomplish their tasks. These hydraulic actuators, which include, for example, hydraulic cylinders and fluid motors, typically include two fluid chambers disposed on opposite sides of a moveable element. Pressurized fluid is introduced into one of the fluid chambers, which causes the moveable element to move relative to the hydraulic actuator housing.
The moveable element is usually connected to a work implement on the work machine through a rod or shaft. Typically, each hydraulic actuator includes a sealing arrangement that engages the rod or shaft to prevent the pressurized fluid from leaking from the fluid chambers of the hydraulic actuator during use. One such sealing arrangement for a hydraulic cylinder is described in U.S. Pat. No. 6,129,358, which describes a unidirectional rod sealing ring adapted to form a sealed condition.
A sealing arrangement for a hydraulic cylinder may include a series of three seals that are disposed in the cylinder head to engage the shaft proximate exit point of the shaft. The cylinder head typically includes a series of annular grooves, or counter bores, that are configured to receive each of the three seals. The first seal, which is placed closest to the pressurized fluid, is known as a buffer seal. The buffer seal forms a high pressure seal with the shaft to prevent the pressurized fluid from escaping the hydraulic cylinder. Due to the high operating pressures of the hydraulic cylinders, however, some of the pressurized fluid will leak through the buffer seal.
The second seal, which is placed on the opposite side of the buffer seal from the fluid chamber is known as a “U-cup” seal. This seal typically has a notch or groove that forms a “U” shape. This seal provides a second seal to prevent the fluid that has leaked through the buffer seal from escaping the hydraulic cylinder. This fluid is captured in a gap between the buffer seal and the “U-cup” seal and in the notch or groove in the seal. When operating conditions permit, the buffer seal allows the captured fluid to bypass the buffer seal and return to the system.
The third seal, or the outermost seal, is known as a wiper seal. This seal prevents dirt or debris from entering the system and contaminating the fluid. The wiper seal also wipes any remaining fluid from the surface of the shaft. The fluid removed from the surface of the shaft is collected in a gap between the “U-cup” seal and the wiper seal. As additional fluid is captured between these seals, the pressure of the fluid between the seals will continue to build. If the fluid pressure becomes great enough, the force of the pressure may cause the wiper seal to dislodge from its annular groove in the cylinder head. When the wiper seal is dislodged, the cylinder loses its protection from contaminating elements, such as dirt and debris.
The reverse pressure actuated seal and sealing assembly of the present invention is directed to solving all or some of the problems set forth above.